Application Of Two-Dimensional Perovskite Materials In Solar Cells

Energy is one of the important resources which is needed in society development.Among them,solar energy as an inexhaustible clean energy has been widely concerned by researchers.Organic-inorganic hybrid perovskite solar cells because of its low cost and high conversion efficiency is becoming a hot spot of research.After the development of organic-inorganic hybrid perovskite solar cells for a short period of ten years,the photoelectric conversion efficiency has exceeded 25%,which is close to that of single-crystal silicon solar cells.In order to improve the stability of perovskite solar cells,it is necessary to research from the aspects of material,structure and preparation technology.In this paper,the contact and energy level matching between perovskite layer and hole transport layer are improved by modifying the two-dimensional perovskite material,so as to improve the stability and performance of the device.The main content of this paper is:1.The enhancement of both performance and stability of organic-inorganic hybrid perovskite solar cells is reported by employing two-dimension(2D)/three-dimension(3D)planar perovskite films.The 2D/3D planar perovskites combine the advantages of the high-performance from the 3D perovskite and the stability from 2D-perovskite.It is found that the benefits of the 2D perovskite are attributed to ultrathin coverage on the 3D perovskite surface,which not only passivates the grain boundaries of the underlayer 3D perovskite,but also aligns the energy level between the perovskite and hole transport layers from a microscopic point of view.This work demonstrates that modulating2D/3D planar films by hybridizing different species of perovskite is a feasible way to simultaneously enhance both efficiency and stability of perovskite solar cells.2.All inorganic Cs Pb X₃ perovskites have gained great attentions owing to their excellent carrier transport property and thermal stability.However,the presence of X vacancies in the Cs Pb X₃lattice results in high trap density within Cs Pb X₃ films,and subsequently affects the photovoltaic performance of solar cells.Here,we use phenylethylammonium iodide(PEAI)and phenylethylammonium bromide(PEABr)to manipulate the film quality of inorganic perovskites,which significantly improve the moisture-resistance of the Cs Pb I₂Br film and photovoltaic performance.It is found that there is no so-called two-dimensional(PEA)₂Pb I₄ and(PEA)₂Pb Br₄materials formed after a high temperature annealing,but iodine or bromide vacancies within Cs Pb I₂Br can be filled by external anions.The fused grain boundaries render the larger grains with a low trap density,thereby improving the perovskite phase stability and the device efficiency of the Cs Pb I₂Br solar cells.This work shows that the use of high temperature environments to fill vacancies with external anions can promote highly efficient and stable perovskite photovoltaics.3.At present,PTAA and spiro-OMe TAD are the most used hole transport materials for perovskite solar cells.However,these materials are expensive which are not conducive to the development of commercialization,and need to introduce hygroscopic dopants such as lithium salts which are very unfavorable to the wet-resistance of devices.In this experiment,P3HT with low cost,easy to manufacture and good photoelectric performance was used as the hole transmission material,but the efficiency of the device was low.In this paper,the two-dimensional perovskite material PEAI is used as the modification layer between perovskite and P3HT to promote the self-assembly process of P3HT and improve the performance of the device,and the PEAI organic cation is used as a hydrophobic group to improve the stability of the device.This work shows that the self-assembly process of tuning the hole transport layer using a two-dimensional perovskite material with a wideband gap improves the photoelectric efficiency and stability of perovskite solar cells.